U.S. patent number 5,015,622 [Application Number 07/422,542] was granted by the patent office on 1991-05-14 for multidirectional/rotational superconductor motor.
This patent grant is currently assigned to Alfred University. Invention is credited to William B. Carlson, Walter A. Schulze, Jr., Xingwu Wang, Raymond C. Ward.
United States Patent |
5,015,622 |
Ward , et al. |
May 14, 1991 |
Multidirectional/rotational superconductor motor
Abstract
A contactless, multi-dimensional small stepper motor with a
maximum dimension of less than about 10 centimeters is described.
The motor contains at least one magnetized article, at least one
superconductive primary suspending element, and at least two
primary conductive elements. Each of the primary conductive
elements is separated from each adjacent primary conductive element
by a distance of from about 0.01 to about 10 millimeters.
Inventors: |
Ward; Raymond C. (Alfred,
NY), Wang; Xingwu (Alfred, NY), Carlson; William B.
(Alfred, NY), Schulze, Jr.; Walter A. (Alfred Station,
NY) |
Assignee: |
Alfred University (Alfred,
NY)
|
Family
ID: |
23675354 |
Appl.
No.: |
07/422,542 |
Filed: |
October 17, 1989 |
Current U.S.
Class: |
505/166;
310/12.21; 310/12.31; 310/12.32; 310/90.5; 505/852; 505/876 |
Current CPC
Class: |
H02K
41/03 (20130101); H02K 55/00 (20130101); H02N
15/04 (20130101); H02K 99/00 (20161101); H02K
2201/18 (20130101); Y10S 505/876 (20130101); Y10S
505/852 (20130101) |
Current International
Class: |
H02K
57/00 (20060101); H02K 55/00 (20060101); H02K
41/03 (20060101); H02N 15/04 (20060101); H02N
15/00 (20060101); H92K 041/00 (); H92K
055/00 () |
Field of
Search: |
;310/12,90.5
;505/1,852,876,877,878 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Stephan; Steven L.
Assistant Examiner: Jones; Judson H.
Attorney, Agent or Firm: Greenwald; Howard J.
Claims
We claim:
1. A contactless, multi-dimensional small stepper motor with a
maximum dimension of less than about 10 centimeters for converting
electrical energy to mechanical energy which causes movement of at
least one transportable, magnetized article, wherein said motor
comprises at least one superconductive primary suspending element,
at least two primary conductive elements, at least one
transportable magnetized element, means for supplying electrical
energy to at least one of said primary conductive elements, means
for cooling said superconductive primary suspending element, means
for causing the movement of said article, and means for stopping
the movement of said article, wherein:
(a) said superconductive primary suspending element is comprised of
at least 50 volume percent of superconductive material, wherein
said supercondutive material:
1. has a first critical field value greater than about 10 Gauss, a
second critical field value of at least one Tesla, and a critical
temperature greater than 35 degrees Kelvin; and
2. said superconductive material has a flux penetration ratio of
from about 0.01 to about 0.1;
(b) each of said primary conductive elements is separated from each
adjacent primary conductive element by a distance of from about
0.01 to about 10 millimeters; and
(c) the largest dimension of said transportable, magnetized article
is no greater than 1 centimeter; and
(d) said magnetized article has a magnetic moment between said
first critical field value and said second critical field
value.
2. The stepper motor as recited in claim 1, wherein said
superconductive material has a critical temperature of at least
about 77 degrees Kelvin.
3. The stepper motor as recited in claim 2, wherein said
superconductive material is a Type II superconductor.
4. The stepper motor as recited in claim 3, wherein said primary
conductive elements consist esentially of material selected from
the group consisting of copper aluminum, silver, gold, and
superconductor material.
5. The stepper motor as recited in claim 4, wherein said conductive
elements consist essentially of a material selected from the group
consisting of copper and silver.
6. The stepper motor as recited in claim 4, wherein said conductive
elements consist essentially of magnet wire.
7. The stepper motor as recited in claim 6, wherein said magnet
wire has a gauge of from about 20 to about 40.
8. The stepper motor as recited in claim 5, wherein said conductive
elements consist of wires with a gauge of from about 20 to about
40.
9. The stepper motor as recited in claim 8, wherein said conductive
elements are electrically insulated from said superconductive
primary suspending element.
10. The stepper motor as recited in claim 9, wherein said
conductive elements have a maximum cross-sectional dimension of no
greater than about 5 millimeters.
11. The stepper motor as recited in claim 10, wherein said
conductive elements have a maximum cross-sectional dimension of no
greater than about 3 millimeters.
12. The stepper motor as recited in claim 11, wherein said
conductive elements have a maximum cross-sectional dimension of no
greater than about 1 millimeter.
13. The stepper motor as recited in claim 1, wherein the levitation
height of said superconductive material is at least about 0.1
centimeters.
14. The stepper motor as recited in claim 1, wherein the levitation
height of said superconductive material is at least about 0.7
centimeters.
15. The stepper motor as recited in claim 1, wherein said means for
cooling said superconductive primary suspending element is a
chamber partially filled with cryogenic coolant.
16. The stepper motor as recited in claim 15, wherein said
cryogenic coolant is liquid nitrogen.
17. The stepper motor as described in claim 1, wherein each of said
superconductive primary suspending elements are electrically
insulated from each of the other of said superconductive primary
suspending elements.
18. The stepper motor as described in claim 17, wherein at least
two of said primary conductive elements are connected to at least
one of said superconductive primary suspending elements.
19. The stepper motor as described as described in claim 17,
wherein said superconductive primary suspending elements are so
configured and attached to each other that they define a
three-dimensional grid.
20. The stepper motor as described in claim 1, wherein said primary
conductive elements are physically attached to an element selected
from group consisting of at least one of said primary suspending
elements, at least one of said means for cooling said
supercondutive primary suspending elements, and mixtures thereof.
Description
FIELD OF THE INVENTION
A small stepper motor containing a superconductive element for
suspending a magnetized article, and means for causing two- or
three-dimensional movement of the magnetized article.
BACKGROUND OF THE INVENTION
Stepper motors which cause a certain amount of motion in response
to a an input electrical pulse are well known to those skilled in
the art. They are disclose, for example, in P. C. Sen's "Principles
of Electric Machines and Power Electronics" (John Wiley and Sons,
New York, 1989). The stepper motors disclosed in the Sen book have
contacts between stationary and moving parts and, thus, lose a
substantial amount of energy to friction.
A superconducting stepper motor is described in an article by
Andrew A. Moultrhop et al. entitled "Superconducting stepper
motors," Rev. Sci. Instrum. 59 (4), April, 1988. The motor
described in this paper is rotary, and it contains a several coils,
each of which have many windings. This motor is not capable of
moving an object in planar motion.
A linear motor with superconductive elements is disclosed in
Japanese patent number 63-262056. The motor of this patent contains
large stator coils, which necessitates a relatively large size for
the motor and limits its usefulness in applications requiring small
stepper motors.
Another linear motor with superconductive elements is disclosed in
Japanese patent number 1034171. The motor of this patent also
contains large coils, necessitates a large size, and limits its
usefulness in applications requiring smaller size.
Superconducting tooth structures for electromagnetic devices are
described in IBM Technical Disclosure Bulletin Vol. 31 No. 9
(February, 1989). The apparatus of this invention does not appear
to be able to readily move an object in two- or three-dimensions
within a relatively small space.
It is an object of this invention to provide a contactlass stepper
motor which is substantially more efficient than most of the prior
art stepper motors.
It is another object of this invention to provide a small,
contactless stepper motor which has a maximum dimension of less
than 10 centimeters and which is able to move a magnetized object
in two- or three-dimensions within a relatively small space.
SUMMARY OF THE INVENTION
In accordance with this invention, there is provided a small,
contactless, multi-dimensional stepper motor. This motor, which has
a maximum dimension of less than about 10 centimeters, contains at
least one superconductive element, at least two conductors, and a
transportable, magnetized element.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more fully understood by reference to
the following detailed description thereof, when read in
conjunction with the attached drawings, wherein like reference
numerals refer to like elements and wherein:
FIG. 1 is a perspective view of one preferred embodiment of the
linear motor of the invention;
FIG. 2 is a top view of the embodiment of FIG. 1;
FIG. 3 illustrates the electromagnetic fields caused by current
flowing through a conductor and the motion such fields cause in a
magnetized object;
FIG. 4 illustrates the stepwise motion of a magnetized object which
may be created in the embodiment of FIG. 1;
FIG. 5 is a top view of a preferred embodiment of the motor of this
invention in which two-dimensional motion is obtainable;
FIG. 5A is a perspective view of another preferred embodiment of
the motor of this invention in which two-dimensional motion is
obtainable and in which, for the sake of illustration, one of the
superconductive elements is shown in broken-away detail;
FIG. 5B is a partial perspective view of another preferred
embodiment of the motor of this invention in which
three-dimensional motion is obtainable;
FIG. 5C is another partial perspective view of yet another
preferred embodiment of the motor of this invention in which
three-dimensional motion is obtainable;
FIG. 5D is a perspective view of yet another preferred embodiment
of the motor of this invention in which a combination of planar and
vertical motion is obtainable;
FIG. 5E is a perspective view of yet another preferred embodiment
of the motor of this invention in which two-dimensional motion is
obtainable and which operates by a principle different than the
motor of FIG. 1;
FIG. 6 is a cross-sectional view of the embodiment of FIG. 1;
FIG. 7 illustrates the planar motion obtainable with a magnetized
object with the motor of FIG. 5;
FIG. 8 shows the current directions which correspond to the motions
described in FIG. 7;
FIG. 9 is a top view of a single loop coil of the motor of FIG.
5;
FIG. 10 is a perspective view of the embodiment of FIG. 9;
FIG. 11 is a perspective view of yet another preferred embodiment
of the motor of this invention in which two-dimensional motion is
obtainable;
FIG. 12 is a cross-sectional view of a rotational motor;
FIG. 13 is a top view of the embodiment of FIG. 12;
FIG. 13A is a partial top view of the base of the motor of FIG. 12
from which the stator has been omitted for the sake of
simplicity;
FIG. 14 is a cross-sectional view of yet another preferred motor of
the invention in which three-dimensional movement may be
obtained;
FIGS. 15 is a cross-sectional view of the motor of FIG. 14, showing
a different position of the magnetized object caused by the
motor;
FIGS. 16 is a cross-sectional view of the motor of FIG. 14, showing
a different position of the magnetized object caused by the
motor;
FIG. 17 is a force diagram corresponding to the motor of FIG.
14;
FIG. 18 is a cross-sectional view of a preferred embodiment of the
invention which allows stable motion to be achieved;
FIG. 19 is a cross-sectional view of a preferred embodiment of the
invention which allows stable motion to be achieved;
FIG. 20 is a cross-sectional view of a preferred embodiment of the
invention which allows stable motion to be achieved;
FIG. 21 is a two-phase wiring diagram for a synchronous motor;
FIG. 22 is a cross-sectional view of a synchronous motor;
FIG. 22A is a three-phase wiring diagram for a synchronous
motor;
FIG. 23 illustrates mechanical means for cutting a groove into a
superconductive substrate;
FIGS. 24 and 24A illustrate a lithographic method for cutting
grooves into a superconductive substrate;
FIG. 25 is a sectional view illustrating the positions of the
conductors within grooves in a superconductive substrate in one
preferred embodiment of the invention;
FIG. 26 is a partial sectional view illustrating an insulating
layer of one preferred embodiment;
FIG. 27 is a partial sectional view illustrating insulating layers
of one preferred embodiment;
FIG. 28 is a block diagram of one control means which may be used
in the applicants' invention;
FIG. 29 is a schematic of one preferred circuit which may be used
in applicants' devices;
FIG. 30 is a cross-sectional view of one preferred means for
cooling one preferred embodiment of the motor of this
invention;
FIG. 30A is a perspective view of the embodiment of FIG. 30;
FIG. 31 is a partial sectional view of yet another preferred means
for cooling the motors of the invention;
FIG. 32 is a partial sectional view of yet another preferred means
for cooling the motors of the invention;
FIG. 33 is a partial sectional view of yet another preferred means
for cooling the motors of the invention;
FIG. 34 is a partial perspective view of one preferred means for
cooling the motors of the invention; and
FIG. 34A is another partial perspective view of yet another means
for cooling the motors of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
One preferred embodiment of the linear motor of this invention is
illustrated in FIG. 1. Referring to FIG. 1, linear motor 10 is
comprised of superconductive plate 12, or an assembly of
superconductor elements, a multiplicity of conductors 14, and a
permanent magnet 16.
The linear motor 10 is preferably a small motor, but it may have a
range of sizes. In one preferred embodiment, illustrated in FIG. 1,
the length 18 of said plate 12 is from about 1 millimeter to about
10 centimeters, the width 20 of said plate is from about 1
millimeter to about 10 centimeters, and the thickness 22 of the
plate is from about 0.01 microns to about 1 centimeter. It is
preferred that the length 18 of said plate 12 be from about 1
millimeter to about 4 centimeters, the width 20 of said plate be
from about 1 millimeter to about 4 centimeters, and the thickness
22 of the plate be from about 1 micron to about 4 millimeters. In
an even more preferred embodiment, length 18 is from about 2 to
about 3 centimeters, width 20 is from about 2 to about 3
centimeters, and thickness 22 is from about 1 to about 3
millimeters. A motor of proportionally larger or smaller dimensions
also is feasible; this motor may comprise a similar assembly of
elements.
Plate 12 may be of any shape such as, e.g., square, rectangular,
circular, elliptical, irregular, and the like. In one embodiment,
it is preferred that plate 12 be substantially square.
Plate 12 preferably consists essentially of superconductive
material. As is known to those skilled in the art,
superconductivity is that phenomenon in which certain metals,
alloys, compositions, and compounds at relatively low temperatures
lose both electrical resistance and magnetic permeability, i.e.,
have inifinite electrical conductivity. See, e.g., N. I. Sax et
al.'s "Hawley's Condensed Chemical Dictionary," Eleventh Edition
(Van Nostrand Reinhold Company, New York, 1987), into this
specification.
The critical temperature of a superconductor is that temperature at
which superconductivity occurs. It is preferred, in the devices of
this invention, that superconductive material with a critical
temperature no lower than about 77 degrees Kelvin (the boiling
point of liquid nitrogen) be used. In one embodiment, the
superconductive material has a critical temperature greater than
about 85 degrees Kelvin. It will be apparent to those skilled in
the art that these devices will work at temperatures lower than 77
degrees Kelvin.
One class of superconductors which may be used are "Type II"
superconductors with a critical temperature greater than about 77
degrees Kelvin. As is known to those skilled in the art, Type II
superconductors are characterized by first and second values of
critical field, H.sub.c,1 and H.sub.c,2 --in which field
penetration first occurs at the lowest value to result in pinned
fields which persist to much higher H.sub.c,2 levels. See, e.g.,
U.S. Pat. No. 4,797,386 of Gygorgy et al the disclosure of which is
hereby incorporated by reference into this specification, and M.
Tinkham, "Introduction to Superconductivity," Chapter 5, page 143
(McGraw-Hill, Inc., 1975).
The critical current of the superconductive material is an
important parameter. As is known to those in the art, the critical
current is the threshold current flowing through the
superconducting material beyond which superconductivity begins to
deteriorate. See, e.g., the aforementioned Tinkham book.
In an especially preferred embodiment, the superconductor material
12 has a critical temperature of at least about 77 degrees Kelvin,
is a Type II material, and is a ceramic material.
In one preferred embodiment, the superconductor material used in
the invention has specified H.sub.c,1 and H.sub.c,2 properties. The
H.sub.c,1 of these preferred materials is from about 10 to about
100 Gauss. The H.sub.c,2 of these materials is from about 30 to
about 100 Tesla. The second value of the critical field of the
superconductor material is generally at least about 10,000 times as
great as the first value of the critical field of the material.
High-temperature superconductors which may be used in the invention
are described in an article by A. W. Sleight entitled "Chemistry of
High-Temperature Superconductors," Science, Volume 242 (Dec. 16,
1988) at pages 1519-1527.
One preferred class of superconductors, described on pages
1522-1523 of the Sleight article, is of the formula RBa.sub.2
Cu.sub.3 O.sub.6+x, wherein x is from about 0.5 to about 1.0 and R
is a rare earth element selected from the group consisting of
yttrium, gadolinium, lanthanum, europium, holmium, and the like. In
one preferred embodiment, R is yttrium.
Another preferred class of superconducting materials is of the
formula (AO).sub.m M.sub.2 Ca.sub.n-1 Cu.sub.n O.sub.2n+2, wherein
A is selected from the group consisting of thallium, bismuth, and
mixtures of bismuth and lead, m is from about 1 to about 2 (and
generally is 1 or 2 when A is thallium and is 2 when A is bismuth),
M is selected from the group consisting of barium and strontium,
and n is at least 1. In one preferred embodiment, illustrated on
page 1523 of the Sleight article, A is thallium, m is 2, M is
barium, and n is 3; this composition has a critical temperature of
about 122 degrees Kelvin.
The superconductor used in this invention, when tested in
accordance with a specified test, will have a specified levitation
height. As is known to those skilled in the art, superconducting
materials exhibit the "Meissner effect," which is the exclusion of
a magnetic field from a superconductor. See, e.g., M. Tinkham's
"Introduction to Superconductivity," supra.
As is known to those skilled in the art, levitation height may be
calculated from the following Hellman equation:
wherein d is the levitation height, as measured from the center of
the levitating object to the top surface of the superconductor, in
centimeters; M is the magnetic moment of the levitating object, in
gauss; H.sub.c,1 is the first critical field value, as discussed
hereinabove; L is the thickness of the superconducting material, P
is pi, and is equal to about 3,1416, D is the density of the
levitating object, and g is the gravitational constant, and is
equal to about 9.81 meters per second per second. Reference may be
had to an article by F. Hellman et al. entitled "Leviatation of a
magnet over a flat type II superconductor" (Journal of Applied
Physics, 63 (2), Jan. 15, 1988). The levitation height may be
expressed as a function of the first critical field; it may also be
expressed as a function of the critical current. See, for example,
the aforementioned Tinkham's book and L. C. Davis et al.,
"Stability of magnets levitated above superconductors," Journal of
Applied Physics, 64(8), 15 Oct., 1988.
In the levitation height test used, which determines the levitation
height obtained by a specified magnet with the superconductor
material to be tested, one uses a specified rare earth cobalt
magnet (obtained from the Edmund Scientific Company, 1989 catalog
number D33,168, page 148) which had a magnetic moment of 8,200
gauss, a mass of 0.24 grams, a diameter of 0.476 centimeters, and a
thickness of 0.159 centimeters. In this test, the superconducting
material is formed into a flat, substantially square shape with a
thickness of about 0.3 centimeter and a width of about 3
centimeters. The superconducting material used in this test is a
bulk material obtained by a solid state reaction method, and the
critical current of it is around 100 to 1,000 amperes per square
centimeter. If different processing techniques are used (such as
thin film formed by evaporation), then the critical current will be
different. In one embodiment, where the thin film is formed by
electron beam evaporation, the critical current will be from 10,000
to about 100,000 amperes per square centimeter. With such a film,
with a thickness of about 1 micron, levitation of the specified
permanent magnet also can be achieved.
The levitation height obtained with the superconductor flat square
which is tested in accordance with this procedure is preferably at
least about 0.7 centimeters.
If the procedure is changed to vary, e.g., the thickness of the
superconducting square, the density of the levitating object, or
other parameters described in the aforementioned formula, different
levitation heights will result with the same superconductive
material. The levitation height obtained with the superconductor
material in the form of the specified flat square is determined in
accordance with the aforementioned test. In general, in applicants'
system, the levitation height of the system must be at least about
0.1 centimeters.
The stability of magnets levitated above superconductors depends
upon several factors such as the flux penetration and the pinning
effects. See, e.g., an article by L. C. Davis et al. entitled
"Stability of magnets levitated above superconductors," supra.
The pinning force exerted by the magnetized object upon the
superconductive plate may be estimated by the following formula of
Davis:
wherein F.sub.D is the pinning force (in Newtons), L is the
levitation height of the system (in meters), U.sub.O is the
magnetic permeability of free space (in tesla-meters/ampere),
H.sub.max is the maximum magnetic field (in amperes/meter), and
J.sub.c is the critical current of the superconductor material (in
amperes/square meter). Reference may be had to L. C. Davis et al.'s
"Stability of magnets levitated above superconductors," page 4212,
supra.
The pinning effect is important with the devices of this invention,
for it helps insure stable levitation of the magnetized article.
Other factors also affect such stability, such as the strength of
the magnetic field around the magnetized article, and/or
electromagnetic field around the conductors, the mass distribution
of the magnetized article, the magnetic moment (which varies with
the geometry of the magnet) of the magnetized article. It is noted
that some residual flux lines may be remained after the magnetic
field is presented near the type II superconductors. Such residual
fluxes can be removed by applying exponentially
decaying-alternating current through the conductors. This technique
is known as the "demagnetization". The flux lines can also be
removed by increasing the temperature of the superconductor beyond
its critical temperature, and then cooling it down below the
critical temperature without the presence of the magnetic
field.
In one preferred embodiment, the superconductor used in the
invention is of the formula YBa.sub.2 Cu.sub.3 O.sub.7-x, the well
known 1-2-3 superconducting phase. This superconducting material is
prepared by a solid state reaction method. Stoichiometric amounts
of yttrium oxide, barium carbonate, and copper oxide are intimately
mixed and ground, and the powder is then calcined in a special
calcination cycle.
In the preferred calcination cycle used by applicants, the material
is first raised from ambient temperature to a temperature of from
about 900 to about 960 degrees centigrade at a rate of from about
100 to about 400 degrees centigrade per hour. It is preferred to
raise the temperature of the material from ambient temperature to a
temperature of from about 910 to about 930 degrees centigrade at a
rate of from about 275 to about 325 degrees centigrade per hour. In
one preferred embodiment, the temperature of the material is raised
to from about 920 to about 930 degrees centigrade at a rate of
about 290 to about 310 degrees centigrade per hour. Once the
material reaches the temperature of from 900 to 960 degrees
centigrade, it is maintained at this temperature for from about 10
to about 15 hours. Thereafter, its temperature is reduced to
ambient at a rate of about from about 100 to about 400 degrees per
hour. In one preferred embodiment the sample is held for 12 hours
at 925 degrees centigrade.
The cooled calcined material is then ground until substantially all
of its particles are smaller than 44 microns (standard US mesh size
325), and then the entire calcination/grinding cycle may be
repeated one or more times.
It will be apparent to those skilled in the art that other
calcination/grinding cycles which improve the homogeneity of the
powder batch also may be used.
Without wishing to be bound to any particular theory, applicants
believe that the use of the grinding/calcination cycle produces a
superconductor with a pure phase. Shaped objects made from material
thus processed are less brittle, or substantially more
suitable.
Any conventional means may be used to prepare the shaped objects.
Thus, for example, one may use the forming processes described in
James S. Reed's "Introduction to the Principles of Ceramic
Processing," (John Wiley and Sons, Inc., New York, 1988).
In one preferred embodiment, the calcined powder is formed into a
shaped object by pressing. The pressing techniques described at
pages 329-355 of said Reed book may be used. In general, in this
embodiment, it is preferred to use a pressing pressure of from
about 6 thousand to about 12 thousand pounds per square inch. In a
more preferred embodiment, the pressure used is from about 7,000 to
about 9,000 pounds per square inch. In general, this pressure is
applied to the powder for from at least about 1 minute and,
preferably, from about 1 to about 3 minutes. With the 1-2-3
calcined powder described above, a pressing time of from about 1 to
about 2 minutes, a pressure of about 8,000 p.s.i., and a press and
release sequence of about 3 times, is suitable.
The pressed body is then preferably sintered under specified
conditions to yield a sintered body with substantially no internal
deformations. Sintered bodies will have the suitable flux pinning
characteristics and desired mechanical strengths. A unique
sintering cycle is utilized for this purpose. During this entire
sintering and annealing cycle, the pressed body is maintained under
a flowing oxygen-containing gas while being sintered. The oxygen
containing gas may be pure oxygen. The oxygen-containing gas
preferably is at a pressure of at least about 1 atmosphere, and it
is flowed over the pressed plate(s) at a rate of from about 1 to
about 100 cubic centimeters per minute.
It is preferred to raise the temperature of the formed body from
ambient to a temperature of from about 930 to about 970 degrees
centigrade at a rate of less than about 300 degrees centigrade per
hour while the pressed body is under a flowing, oxygen-containing
gas. It is more preferred to raise the temperature of the body from
ambient to a temperature of from about 940 to about 960 degrees
centigrade at a rate of less than about 250 degrees centigrade per
hour.
Once the pressed body has reached the sintering temperature, it is
maintained at this temperature under flowing oxygen-containing gas
for at least about 12 hours. It is preferred to maintain the body
at this temperature for from about 22 to about 26 hours. In one
embodiment, the pressed body is maintained under these conditions
for about 24 hours.
After the pressed body has been sintered under the aforementioned
conditions, it is then cooled to a temperature of from about 450 to
about 650 degrees centigrade at a rate of less than about 150
degrees centigrade per hour while under said flowing
oxygen-containing gas. In one preferred embodiment, the sintered
body is cooled to a temperature of from about 450 to about 550
degrees centigrade at a rate of from about 90 to about 110 degrees
centigrade per hour.
After the sintered body has been cooled to a temperature of from
about 450 to about 550 degrees centigrade, it is annealed at this
temperature while under said flowing oxygen-containing gas for at
least about 5 hours and, preferably, from about 5.5 to about 6.5
hours.
In the embodiment involving the 1-2-3 superconducting phase of
yttrium/barium/copper, described above, the superconducting
orthorhombic phase is formed during this annealing process. After
the material has been annealed, it is then cooled to ambient
temperature; it is preferred, though not essential, that this
cooling step occur under flowing oxygen-containing gas. The cooling
to ambient temperature occurs at a rate of less than about 100
degrees centigrade per hour. In one preferred embodiment, the
cooling rate is about 60 degrees centigrade per hour.
Referring again to FIG. 1, conductors 14 conduct electric current
and, in such process, generate electromagnetic fields around them
in accordance with Ampere's Law. See, e.g., pages 350-365 of Robert
L. Weber et al.'s "College Physics," Third Edition (McGraw-Hill
Book Company, New York, 1959).
Conducting means 14 may be any conducting material. Thus, by way of
illustration and not limitation, conducting means 14 may consist
essentially of copper, aluminum, silver, gold, and/or another
superconductor. The conducting means can be of substantially any
shape. Thus, it may be in the form of a wire or strip which has a
circular, square, rectangular, or irregular cross-section.
In one preferred embodiment, copper or silver wire is used. In this
embodiment, it is preferred that the gauge of the wire be from
about 20 to about 40. As is known to those skilled in the art, the
gauge of a wire conductor is specified as "American Wire Gauge
Conductor Series"; and an AWG number of 30, e.g., refers to 30
gauge wire. A table describing the AWG conductor series appears,
e.g., on page 766 of Herbert W. Jackson's "Introduction to Electric
Circuits," Sixth Edition (Prentice Hall, Englewood Cliffs, N.J.,
1986).
In one embodiment, one may use a wire conventionally referred to as
"magnet wire" with a gauge of from about 20 to about 40; see, e.g.,
page 793 of catalog 110 Newark Electronics, Chicago, Il.
Conducting means 14 may be attached to plate 12 by any conventional
means. It is essential, however, that an insulating barrier shield
conducting means 14 from plate 12.
In one embodiment, conducting means 14, in the form of wire, is
glued to the surface of plate 12. In another embodiment, conducting
means 14 is inserted into grooves cut into the surface of plate 12.
In yet another embodiment, conducting means 14 is deposited by
means of thermal vapor deposition, sputtering, electron beam vapor
deposition, flame or plasma spray, thick film printing, etc. upon
plate 12. See, e.g., P. Moran's "Hybrid Microelectronic
Technology," Electrocomponent science monograms, vol. 4 (Gordon and
Breach Science Publishers, New York, 1984). Means of connecting
conducting means 14 to plate 12 will be discussed later in this
specification.
The separation between adjacent conducting means 14 should be
relatively small. It is preferred that the distance between
adjacent conducting means 14 be no greater than about 1
centimeter.
The conducting means 14 generally will have a largest
cross-sectional dimension which does not exceed about 5 millimeter.
The largest cross-sectional dimension is the longest line which may
be drawn from any point on the periphery of the cross-section to
any other point on the periphery. In the case of a circle, e.g., it
will be the diameter.
It is preferred that the largest dimension of the cross-sectional
area of conducting means 14 be no greater than about 3 millimeters.
In one embodiment, such largest dimension is no greater than about
1 millimeter.
Linear motor 10 comprises a means for generating an electromagnetic
field. These means include, in addition to conducting means 14, the
connecting leads from a current source. Thus, referring to FIG. 2,
which is a top view of the linear motor of FIG. 1, leads 22, 24,
and 26 conduct current into wires 14, and leads 28, 30, and 32
conduct current away from conductors 14.
Leads 22 and 28 may be connected to conductor 14 by any
conventional means known to those skilled in the art. Thus, the
leads may be conducted to the conductor 14 by soldering, by
mechanical means (such as clips), and the like.
In one embodiment, not shown, one or more of the leads is an
integral part and extension of conductor 14.
Referring again to FIG. 1, linear motion of magnet 16 is caused by
electromagentic fields around one or more of conductors 14. Some of
the forces causing said motion are illustrated in FIG. 3. By
controlling the magnitude, direction, and timing of said fields,
magnet 16 may be caused to move in a forward and/or backwards
direction.
It is apparent to those skilled in the art that there are several
factors affecting the performance of the motors, such as the
geometry, mass distribution, and the strength of the magnetic
moment of the magnetized article. In one preferred embodiment, such
magnetized object can be formed according to some engineering
designs. For example, one may cut a disc-shaped magnet into two
half-moon shaped magnets. Due to gravity force, the curved edge
side will be facing downwards. When the north and south poles are
aligned perpendicularly to the flat surfaces, the magnet will be in
a stable configuration.
In another application of the devices the magnetized article(s) may
have random shape(s), where the devices can be used as filters.
FIG. 3 illustrates the electromagnetic field produced by passing a
current through a wire. Referring to FIG. 3, when current flows in
direction 38 into the plane of the paper, then the electromagnetic
field shown with field direction 36 is produced. When magnet 16 is
disposed above and to the left of wire conductor 14, it will be
forced to the right, as indicated by arrow 40.
FIG. 4 is a top view of the linear motor of FIG. 1 from which
details of superconducting plate 12 have been omitted for the sake
of simplicity. When the current flows in the direction indicated as
34 in FIG. 3, then a magnet 16 will be moved across conductors 14
stepwise in direction 40. In this embodiment, it is preferred to
apply pulsed current first to the conductor 14 nearest magnet 16,
and then to the next nearest one, and then to the next nearest one,
etc. The magnet 16 is thus moved stepwise across the conductors 14
as they each, in their turn, attracts it.
It is also possible to create a repulsive force rather than an
attractive force to achieve the desired motion. In addition, a
combination of the attractive and repulsive forces can be utilized.
The attractive and/or repulsive forces can be produced from a
pulsed DC current, an alternating current, or the combination of
both.
FIG. 5 illustrates another embodiment of the invention, a planar
motor. In this embodiment, the conductors are dispoosed above
superconductive plate 12 in a grid pattern.
Referring to FIG. 5, conductive strips 14 are arranged
substantially horizontally across the top of superconductive plate
12. Each of these strips 14 may be connected to suitable leads,
such as leads 22, 28, 50, and 52.
Conductive strips 42 are arranged substantially perpendicularly to
strips 14 and also may be connected to suitable leads, such as
leads 46 and 48.
Conductive strips 42 are insulated from conductive strips 14, which
in turn are insulated from the top surface of superconductive plate
12.
In the embodiment of FIG. 5, conductors 14 and 42 have dimensions
similar to those specified for the conductors of the linear motor
of FIG. 1. Each of conductors 14 and 42 may have substantially the
same dimensions; or they may be different. The spacing between a
set of horizontal conductors 14, and the spacing between a set of
vertical conductors 42, is substantially similar to the spacing of
the horizontal conductors 14 of the linear motor of FIG. 1.
One embodiment of the insulating barrier which exists between
conductors 14 and 42 is illustrated in FIG. 6. Referring to FIG. 6,
insulating barrier 44 is disposed between conductors 14 and 42.
Another insulating barrier, not shown, is disposed between the top
surface of superconductive plate 12 and conductors 14.
In another embodiment of the invention, shown in FIG. 5A,
superconductive plate 12 is comprised of a multiplicity of
substantially square superconductive sections 49 which are
separated from each other by electrical insulation. The motor of
this embodiment may be substantially larger than the linear motor
of FIG. 1. (An alternative design of FIG. 5A is to use
superconducting wires rather than superconductive cells.) By
applying current 47 to one of said insulated squares 49, the
superconductivity of that square 49 will be substantially reduced
and/or destroyed as long as the current is larger than the critical
current of the superconductive cell. Current can be applied to
different isolated squares at different times to cause the Meissner
effects of such square to vary. A magnet levitating above said
insulated square will no longer be repelled once the
superconductivity of a particular square is destroyed. The magnet,
thus, can be caused to hop from the top of one cell whose
superconductivity has been destroyed to another by selectively
applying current to said cells; and it can be caused to move in a
one and/or two dimensional pattern. By using the similar means of
control, additional degrees of freedom of motion are also possible.
For example, motion along the vertical direction normal to the base
plate 14 may be obtained.
Referring to FIG. 5B, which is partial perspective view of a
three-dimensional motor of this invention, rods 51 consist of
superconductive material described above. The rods may be coated
with one or more strips of conductors (not shown) by means such as
pasting, evaporating, inserting, or otherwise attaching the
conductors to the superconducting rods. A magnetized object, not
shown, can move in a three-dimensional pattern within the space
defined by the rods in response to current pulses delivered to
selected portions of the rods by the conductive wires.
Another three-dimensional motor embodiment is illustrated in FIG.
5C. In this embodiment, superconductive blocks 53 are supported by
frame members 55. Conductors, not shown, are attached to the frame
members 55. A magnetized object, not shown, within the space
defined by the frame can be moved in any direction or combination
of directions by passing current pulses to the selected portions of
the frame at appropriate times.
Yet another three-dimensional motor embodiment is illustrated in
FIG. 5D. In this embodiment, plates 57 consist essentially of the
aforementioned superconductive material. Conductors, not shown, are
attached to these plates (see, e.g., FIG. 5). Each of plates 57 is
comprised of at least one orifice 61. The magnetized object 16 may
be moved above each plate 57, and/or through orifice 61 of each
plate along directions 63. This device can be used as a filter, in
which case some selected particles will be deposited into or taken
away from container 59.
In yet another embodiment, shown in FIG. 5E, one electromagnetic
coil 65 is placed under each of a series of electromagnetically
isolated superconductive cells 49 which are in a matrix format. The
motor of this embodiment may be substantially larger than the
linear motor of FIG. 1. By passing current through a selected one
of the coils, a magnetic field will be produced around that coil.
When the field is larger than the first critical field of
superconductor, H.sub.c, .sub.1, the superconductivity of the
corresponding cell will be reduced or destroyed. The magnet above
the cell whose superconductivity has been reduced or destroyed will
tend to be attracted by the force of gravity towards the surface of
such cell. If an electromagentic field is applied to one or more
adjacent cells, and the current to the first cell is stopped, then
the magnet will be moved to the next selected cell in a hopscotch
manner.
Referring again to FIG. 6, insulating barrier 44 is disposed
between conductor 14 and conductor 42. Any suitable insulating
material may be used to form the insulating barrier. Thus, for
example, barrier 44 may be an organic (such as epoxies) or an
inorganic (such as glasses and crystalline materials).
The insulating layers can form either around conductors 14 and/or
42, or just in the areas needed to insulate them from each other
and the superconductor plate 12. Other means can also be used to
form insulating barrier 44, such as the processes used to construct
the conducting means 14 described hereinabove.
In one preferred embodiment, the insulating material is an epoxy
resin. As is known to those skilled in the art, epoxy resins have
in their molecules a highly reactive oxirane ring. See, e.g., pages
287-289 of George S. Brady et al.'s "Materials Handbook", Twelfth
Edition, (McGraw-Hill, New York, 1986). One preferred epoxy resin
adhesive useful for insulating and joining conductors 14, 42 and
superconductor 12 is "1266 Epoxy A and B" which is manufactured by
the Emerson and Cuming Company of Massachusetts and is sold by Dean
Co. of Ithaca, N.Y. Other means of insulating conductors 14 and/or
42 will be discussed later in this specification with relation to
FIGS. 25, 26, and 27.
FIG. 7 illustrates some of the ways in which a magnet may be moved
across the planar motor of FIG. 5. Referring to FIG. 5, current may
be introduced into horizontal conductors 14 (via leads 22, 28, 50,
and 52) and vertical conductors 42 (via leads 46 and 48). Referring
to FIG. 7, the magnet may be placed in position 54 substantially
perpendicular to lead 52 and parallel to lead 46. When current is
passed through lead 48, then the magnet moves from position 54 to
position 56, being attracted by the electromagentic field around
conductor 42 (see FIG. 5). When the magnet reaches position 56, the
current through lead 48 may be turned off.
When the magnet is in position 56, it may be rotated 90 degrees to
position 59 by applying current through lead 52. Thereafter, the
magnet may be moved to position 60 by applying current through lead
50. Again, once the magnet reaches position 60, the current through
lead 50 should be turned off.
In a similar manner, the magnet may be rotated 90 degrees from
position 60 to position 62 by applying current through lead 48.
Thereafter, when it is in position 62, the magnet may be moved to
position 64 by passing current through lead 46, rotated 90 degrees
to position 66 by passing current through lead 50, and moved to
position by passing current through lead 52. This procedure may be
repeated, modified, interrupted, etc., to cause the magnet to move
in different directions at different times.
As will apparent to those skilled in the art, a magnetized object
may be caused to spin by the motor of this invention from, e.g.,
positon 56 to 59, then back to 56, then to 59 again. Other movement
patterns may also be used depending upon the current furnished to
the motor and the manner in which it is furnished.
One may cause spinning of the magnetized object by appropriate use
of direct current pulses. Alternatively, or additionally, such
spinning motion may be caused by use of alternating current.
Referring to FIG. 8, it will be seen that the current in conductor
14 can go in one of two different directions 34, as can the current
in conductor 42 (in directions 59). It will be apparent to those
skilled in the art that the polarity of the current supplied to
said leads can readily be reversed by conventional control
means.
FIG. 9 illustrates an embodiment of the invention in which a
single-loop solenoid is formed from conductors 14 and 42 by
selectively applying current to the leads of such conductors. This
Figure is a top view of the apparatus of FIG. 5 from which the
superconducting plate 12 has been omitted for the sake of
simplicity.
Referring to FIG. 9, magnet 16 is attracted by the magnetic fields
of conductors 14 and 42. Current is supplied to conductors 14 and
42 in such a manner and at such times that the current direction
34, 58, 34, and 58, is counterclockwise. Means for supplying such
counterclockwise current through the leads of conductors 14 and 42
are well known to those skilled in the art. See, e.g., Sybil B.
Parker's "McGraw-Hill Encyclopedia of Electronics and Computers"
(McGraw-Hill Book Company, New York, 1984).
FIG. 10 illustrates the magnetic flux lines 36 created by the
solenoid of FIG. 9. In the configuration depicted by this Figure,
magnet 16 is attracted by the solenoid.
FIG. 11 illustrates another embodiment of the invention in which
conductors 70 and 72 are arranged in a diagonal pattern across the
top of superconducting plate 12. It will be apparent to those
skilled in the art that, in addition to the two patterns of
conductors illustrated in the Figures, many other configurations
may be used. Thus, e.g., the conductors may be curved, bent, spaced
unequally from each other, spaced equally from each other,
irregularly configured, and the like.
FIG. 12 illustrates a rotational motor. In the embodiment of this
Figure, superconductive U-shaped stator has a multiplicity of
conductors 81 (shown in FIG. 13A) across its surface. Disposed
above the superconductive surface is a magnetic rotor comprised of
magnets 78, connecting arms 80, joint assembly 82, shaft 84, and
load assembly 86. Each of the magnets 78 is affected by the
electromagnetic fields created around the conductors 81 (shown in
FIG. 13A); and, by suitable introduction of current through some of
wires 81 at different times, the motor may be caused to rotate. The
motion is confined in the U-shaped stator. This kind of motor is
different from the conventional motors described by the Sen's book,
supra.
By suitable processing techniques, superconductive materials can be
formed into desired configurations, which will provide necessary
magnetic field confinement of the magnetized object. Thus the
orientation and/or positioning of the magnetized object can be
controlled. Referring to FIG. 12, the confinement of the magnetic
rotator (magnets 78) is achieved by making a U-shaped stator.
Referring to FIG. 7, for example, the proper orientation and/or
positioning of magnet 68 can be controlled by flux pinning,
switching of electromagnetic field, and/or the geometrical
configurations.
FIG. 13 is a top view of the rotational motor of FIG. 12, showing
that it is comprised of four magnets 78. As will be apparent to
those skilled in the art, more or fewer magnets may be used. It is
preferred, for purposes of rotational stability, to utilize at
least four magnets in this configuration.
Referring to FIG. 13A, it will be seen that the conductors are so
spaced on the surface of superconductor stator 76 that they tend to
induce rotational motion in said rotor when pulsed current is
sequentially passed through adjacent conductors. It will be
apparent to those skilled in the art that the radial pattern of
conductors shown in FIG. 13A is only illustrative, and that many
other patterns will suffice to induce rotational motion in a rotor
similar to that shown in FIGS. 12 and 13. It will also be apparent
to those skilled in the art that other rotors may be used.
FIG. 14 illustrates a device for permitting three-dimensional
motion in a magnet. The apparatus of this figure is comprised of
super conductive plates 12, each of which is attached to a
multiplicity of conductors 42. Magnet 16 is disposed between the
top and bottom plates 12. In the embodiment illustrated in this
Figure, current passing through left conductor 42 of bottom plate
12, in direction 88 (into the plane of the paper) will attract the
north pole of magnet 16 and pull such magnet. A dashed block shown
in this Figure illustrates the next location of the magnet 16,
which is displaced both laterally and longitudinally from the
original position of the magnet.
FIG. 15 shows the magnet 16 having moved to the position depicted
by the dashed block of FIG. 14. In the embodiment of FIG. 15,
current is flowing through middle conductor 42 of the top plate 12
in the direction 90, away from the plane of the paper. A dashed
block shown in this FIG. 15 illustrates the next position of the
magnet 16, which is displaced both laterally and longitudinally
from the position of FIG. 15.
FIG. 16 shows the magnet having moved to the position depicted by
the dashed block of FIG. 15. In the embodiment of this Figure,
current is flowing through the right conductor 42 of the bottom
plate 12 in the direction 92 into the plane of the paper.
It will be apparent to those skilled in the art that a substantial
number of different movements of the magnet 16 can be caused to
occur by varying the timing, type, and amount of current passing
through bottom and top conductors. Although the Figures have only
illustrated current flowing through one conductor at a time, it is
apparent that current may flow through more than one of such
conductors, and that the magnet may be caused to move in a straight
and/or curved path.
In one embodiment, not shown, one or both of top and bottom
superconductive plates 12 will have the grid pattern depicted in
FIG. 5. In another embodiment, not shown, one or both of the
superconductive plates will have the diamond pattern depicted in
FIG. 11. In yet another embodiment, not shown, one or both of the
superconductive plates will have the radial pattern shown in FIG.
13A. Other combinations of patterns will be apparent to those
skilled in the art. With one or more of these arrangments, the
magnet 16 may be caused to move in one, two, or three
dimensions.
FIG. 17 is a force diagram illustrating forces which typically act
upon magnet 16 when it is in the configuration depicted in FIG. 15.
Force 94 represents the force of a gravity and, in addition, a
small pinning force due to flux trapping in bottom superconductive
plate 12; such a pinning force was discussed in an earlier portion
of this specification and is referred to in the Davis et al. paper
mentioned therein. In the configuration of FIG. 15, the bottom
plate 12 is preferably constructed so that it has many fewer
pinning centers than the top plate 12.
Force 96 is the attractive force between the magnet and the
electromagnetic field created by the current through conductor 42
in direction 90 (see FIG. 15).
Force 98 is the pinning force on the magnet due to flux pinning
caused by the "dirtiness" of the top superconductive plate 12. Flux
pinning of this sort was discussed by a paper by P.N. Peters et al
entitled "Observation of enhanced properties in samples of silver
oxide doped YBa.sub.2 Cu.sub.3 O.sub.x " (Applied Physics Letters,
52 [24], Jun. 13, 1988). Such "dirtiness" in a superconductor
refers to the presence of an increased number of pinning centers.
One can increase the number of pinning centers in a superconductor
by well known means. Thus, for example, one may dope the
superconducting powders used to make the shaped object with silver
oxides (see, e.g., the Peters et al. paper). Alternatively, one may
melt the pellet used to make the superconductive plate at a very
high temperature (in excess of about 1,100 degrees centigrade) and
then quench it to a lower temperature (about ambient) at a rate of
at least 1000 degrees per minute; this treatment creates some
non-superconducting phases such as a yttrium-2, barium-1, copper-1
phase.
Force 100 is the net Meissner force from the bottom and the top
superconductive plates. Because the top superconductive plate is
preferably designed to be much "dirtier" than the bottom (and to
thus contain less superconducting phase), the Meissner effect from
the bottom plate is substantially stronger than that from the top.
In general, the Meissner effect from the bottom plate is at least
about 2 times as great as the Meissner effect from the top plate in
this embodiment.
FIG. 18 illustrates a stepped linear motor with increased
stability. In the embodiment of this Figure, connecting means 102
is attached to four magnets 16; the use of a multiplicity of
magnets in the motor of this embodiment provides increased
stability. As is shown in this Figure, the interior conductors 42
closest to the inside magnets 16 are activated by passing current
in the direction of 108 (into the plane of the paper). The net
force will move the assembly forward, in direction 104. This will
bring the assembly to a new location (see FIG. 19) where exterior
conductors 42 are now closer to the outside magnets. Now, current
may be passed in direction 108 through exterior conductors 42; and
the assembly will continue to be pulled in direction 104.
FIG. 20 illustrates a two-phase, synchronous alternating current
motor comprised of stator 112 which contains a superconductive
plate and a multiplicity of conductors 114. A magnetic "rotor" 110
is comprised of a multiplicity of magnets 16 joined by a connecting
means. When a suitable, two-phase alternating current is impressed
upon conductors 114, the rotor 110 is caused to move in direction
104.
FIG. 21 is a wiring diagram for the apparatus of FIG. 20. Suitable
alternating currents, each with a voltage of from about 1 to about
10 volts and a frequency of from about 1 herz to about 1,000 herz,
are preferably imposed across input terminals 118 and 120. Each of
these alternating currents is out of phase with each other. In one
preferred embodiment, this phase difference is 180 degrees. The
spacing between the magnets 16 is preferably substantially uniform;
and the spacing between the conductors 114 is preferably
substantially uniform.
As will be apparent to those skilled in the art, by a proper choice
of phase relationships and the polarity of the magnets used, one
can either pull or push the rotor 110 leftwards or rightwards.
In another embodiment, the alternating currents may have phase
differences other than 180 degrees. In these embodiments, it is
preferred that the spacing between the magnets 16 and the spacing
between the conductors 114 should be changed in accordance with the
changed phase difference.
FIG. 22 illustrates a three-phase, linear, synchronous alternating
current motor comprised of elements similar to the apparatus of
FIG. 21. FIG. 22A is a wiring diagram illustrating how to provide
three-phase alternating current to the apparatus of FIG. 22. Three
separate alternating currents with voltages and frequencies
preferably similar to those described for the preferred embodiment
of FIG. 21, are used; these alternating currents are imposed across
terminals 122, 124, and 126, respectively. In one embodiment, each
of the alternating currents imposed across these terminals are
about 120 degrees out of phase; in this embodiment, the spacing
between the magnets is substantially uniform, as is the spacing
between the conductors; however, the spacing between the magnets
need not be the same as the spacing between the conductors. In
another embodiment, the alternating currents imposed acorss these
terminals have phase differences other than 120 degrees; in this
embodiment, the spacing between the magnets and between the
conductors is preferably not uniform.
FIG. 23 illustrates one means of making grooves in the surface of
plate 12 into which conducting wires 14 may be placed. In the
embodiment illustrated in FIG. 23, a cutting device (such as a
diamond saw 130) is used to cut the grooves into the surface of the
plate.
FIG. 24 illustrates another means of making grooves in the surface
of plate 12 by chemical etching. This method is well known to those
skilled in the art; see, e.g., an article by I. Shih et al.
entitled "Chemical etching of Y-Cu-Ba-O thin films" (Applied
Physics Letters 52 [18], May 2, 1988). As is illustrated in FIG. 24
coated with a suitable photoresistive material 132 (such as an
emulsion). This lithographic technique is well known to those in
the art and is described in, e.g., pages 980-982 of Serope
Kalpakjian's "Manufacturing Engineering and Technology,"
(Addison-Wesley Publishing Company, Reading, Mass., 1989).
Referring again to FIG. 24, after photoresistive emulsion 132 has
been coated upon a polished superconductive plate 12, mask 134 is
placed on top of the coated plate 12, and the photoresistive
material is exposed to light (such as ultraviolet light) through
selective openings in mask 134. After development, the surface of
coated plate 112 is then etched, thereby creating grooves, as is
shown as etched plate 138.
FIG. 25 illustrates the placement of insulating material 142 in
between etched plate 138 and conductors 140. In one preferred
embodiment, epoxy adhesive (such as the epoxy 1266 referred to in
another portion of this specification) is applied to the etched
grooves, and then conductors 140 are placed in the grooves and
secured thereto.
FIG. 26 illustrates another preferred embodiment in which an
insulating layer 144 (such as a layer of epoxy resin, or a vapor
deposited layer of insulating material) is bonded to the surface of
plate 12, and thereafter conductors 46 are bonded to insulating
layer 144, preferably by means of evaporation of the conductive
material (such as copper, silver, gold, or aluminum) onto the layer
144. Thus, one may use thermal evaporation, direct current
sputtering, radio frequency sputtering, electron beam evaporation,
flame or plasma spray, thick film processing, and the like, to
deposit the conductors onto the insulating layer 144.
FIG. 27 illustrates an embodiment in which strips of insulating
material 148 are used instead of insulating layer 144, and
conductors 150 are bonded to strips 148, preferably by means of
evaporation.
FIG. 28 illustrates a means of providing suitable direct and/or
alternating currents to the apparatuses described in the prior
figures. Referring to FIG. 28, microcomputer 152 is electrically
connected to control circuit 154 (described in more detail in FIG.
29) to which power is supplied by power supply 156. The output from
circuit 154 is fed to 158, thus causing magnetic assembly 160 to
move in direction 40.
FIG. 29 illustrates one preferred embodiment of control circuit
154. Referring to FIG. 29, control circuit 154 is comprised of
multiduplexer circuit 162, which is electrically connected to
mechanical relays 164 which, in turn, open and close the switch to
the bases of power transistors 170. The outputs from power
transistors 170 is fed through lines 172 to conductors on the
motors. Bias voltage for the power transistors is provided by power
supply 166. Bias for the relays 164 is provided by the power supply
168, which can be obtained from the microcomputer 152 or other
sources.
In one embodiment, not shown, other switching means are substituted
for the mechanical relays shown in FIG. 29.
FIG. 30 illustrates a means of cooling the superconductive material
of plates 12 below their critical temperatures. Referring to FIG.
30, cooling chamber 174 is preferably made of a material with
relatively high thermal conductivity, such as copper. It is
important that, at that portion of the cooling chamber where
contact is made between the chamber and the superconductive motor
assembly, good thermal contact exist and that the materials of the
chamber are such that there is efficient heat transfer between the
superconductive material and the cooling means within chamber 174.
However, in one embodiment, not shown, those portions of the
chamber 174 which are not in contact with the superconductive motor
assembly are made of materials with poor thermal conductivity (such
as stainless steel, which is a metal, and has low thermal
conductivity), and constructed to give a tortuous thermal
conducting path. This will assure poor heat transfer between the
environment outside of the chamber and the other portion of the
chamber, thereby ensuring that the cooling capability of the
cooling means will not be wasted.
The chamber 174 is comprised of inlet 178 which serves to allow one
to insert liquid nitrogen 176 (or other cooling means, such as
liquid helium or its vapor, or other cryogenic cooling means) and
also serves as a vapor outlet. Superconducting plate 175, comprised
of conductors 177, sits upon a portion of chamber 174. It is
essential to insure that there is good thermal contact between
plate 175 and chamber 174 to suitably cool the superconductor. The
cooling apparatus of this Figure is enclosed in protective means
179 designed to minimize heat exchange between the inside of the
enclosure and the outside environment. The preferred embodiment
illustrated in the Figure has a slope inside of the chamber to
allow vapor to escape from the chamber through inlet/outlet
178.
FIG. 30A is a perspective view of the embodiment of FIG. 30.
FIG. 31 illustrates another means for cooling the superconductive
motors. In this embodiment, additional cooling platforms 180 are
used to cool superconductive motor assemblies 182. It is apparent
to those skilled in the arts, that other cooling means can also be
used to cool the motor assemblies 182; for example, cooling
extensions such as metallic ribbons can be used. In principle, any
material with good thermal conductivity can be utilized. The
platforms 180 preferably consist essentially of material with good
thermal conductivity, such as copper. The apparatus of this Figure
allows the operation of several superconductive motor assemblies at
the same time, acting independently or dependently.
FIG. 32 illustrates a means for cooling the three-dimensional
stepped motors illustrated in FIGS. 14, 15, and 16. In this
embodiment, the cooling means is comprised of top cooling platform
184 (to which superconductive plate 188 is attached) and bottom
cooling platform 186 (to which superconducting plate 190 is
attached).
FIG. 33 illustrates another means for cooling superconductive
plates 188 and 190. In one embodiment, this cooling means has a
circular notch; and each of the superconducting motors 188 and 190
may act independently or dependently. In one embodiment, the top
plate of the superconductive motor assembly has a substantially
circular shape, and the bottom plate has a similar shape; the
magnet 16 thus can go in a circular path, which can be a spiral
path.
FIG. 34 and 34A are yet other configurations to provide cooling to
superconducting material 192. A hollow tube or capillary 194 has
coolant inlet 200 and outlet 202. The electrical current can also
be passed through either the walls of tube 194, or conducting
strips attached to the tube 194. The electrical leads are marked as
196 and 198, which can be used in the same configurations as
conductor 14 of FIG. 1, or in similar configurations.
The stepper motor of this invention is contactless. As used in this
specification, the term contactless refers to a motor in which
there is no physical contact between the part being moved (such as
the rotor) and the rest of the motor (such as the stator). Because
applicants' motor is contactless, it has a larger energy conversion
efficiency than prior art stepper motors.
In one embodiment, not shown, the stepper motor of the invention is
encased in a vacuum chamber to reduce the air drag upon the moving
part(s).
The stepper motor of this invention is multi-dimensional, that is,
it has the capability of moving a magnetized object in any one of
the following dimensions: horizontally (x axis), vertically (y
axis), up/down (z axis), circularly (in either two or three
dimensions), spirally (in either two or three dimensions), and the
like. Furthermore, the magnetized object can be moved in an
irregular pattern in either two or three dimensions, one can
alternate the direction of movement in two or more dimensions (and
thus cause spinning), and one can stop and start the motion at any
time and at any point. Unlike prior art motors, the magnetized
object can be moved in an extraordinarily large number of
directions and ways and speeds. This versatility, in addition to
the small size of applicants' motor, makes such motor especially
useful for separation/filtration of magnetized particles, material
handling, pointing, positioning, polar orientation of magnetized
objects, and the like.
In one embodiment, a separation/filtration device can be used to
filter out materials with different magnetic properties which may
exhibit paramagnetism, antiparamagnetism, ferromagnetism,
antiferromagnetism, diamagnetism, ferrimagnetism, etc. The degree
of magnetization of the materials affects the degree to which they
act upon or are acted upon by the device of this invention.
Furthermore, the size and the polar distribution of the particles
also affect the degree to which they interact with the device.
Thus, one may selectively filter out undesired particles based upon
their size and/or the magnetic properties. Such a process may thus
be used to separate minerals, blood cells, and the like.
In another embodiment, a conveyor system comprised of one or more
of the motors of this invention can be used for mass transfer
purposes. The object(s) to be transferred may either be a magnetic
object(s) or a nonmagnetic object(s) encased in or supported by a
magnetized carrier. Alternatively, the superconductive primary
element(s) may be moved, and the magnetized secondary element(s)
may remain stationary.
In a third embodiment, the device of this invention may be used to
perform the functions of pointing and/or positioning and/or polar
orientation which are conducted in a manner substantially similar
to those used in a gyroscope. It will be apparent that the motors
of this invention can be used in devices other than gyroscopes to
perform similar functions.
The motor of this invention has the advantage of low noise and
wear, together with high efficiency because of its contactless
feature. These advantages may be put to good use, e.g., to create
contactless gearing systems. Thus, for example, any of the prior
art gearing systems described, e.g., in pages 400-448 of R. H.
Creamer's "Machine Design," Third Edition (Addison-Wesley
Publishing Company, Reading, Mass., 1984), may be replaced by a
contactless gearing assembly in which the gears interact by the
magnetic principles of this invention. Linear motion may be
achieved in this manner by using the motor, e.g., illustrated in
FIG. 1. Planar motion may be achieved in this manner by using the
motor, e.g., of FIG. 5. Three-dimensional motion may be achieved in
this manner by using the motor, e.g., of FIGS. 5B and 5C.
Rotational motion may be achieved in this manner by using the motor
of, e.g., FIGS. 7 and 12.
In one embodiment, not shown, two or more substantially rectangular
grids with substantially rectangular orifices in them are
positioned facing each other, being separated from each other by
the Meissner effect described above; one of these may be a
magnetized object, and the other of these may comprise
superconductive elements. By the use of applicant's invention,
these grids may be stably diposed in a multiplicity of different
positons vis-a-vis each other, may be moved very precisely to
different positons and/or locations, and may be used to carry other
objects, such as small electronic parts. Thus such grid-motor can
be used in a precision-assembly equipment for mounting miniture
electronic parts. It will be apparent that this embodiment is not
limited to rectangular objects and/or objects with rectangular
orifices.
The stepper motor of this invention is small, that is, its maximum
dimension (taken horizontally, vertically, or up/down) is less than
about 10 centimeters. In one preferred embodiment, the maximum
dimension of applicants' motor is less than about 5 centimeters. In
another embodiment, the maximum dimension of the motor is less than
about 3 centimeters.
In one embodiment, the length and width of the motor are
substantially equal, being from about 0.8 to about 1.2 times each
other.
The motor of this invention is comprised of at least one
superconductive primary suspending element. Such suspending element
is comprised of at last about 50 volume percent of one or more of
the superconductive materials. It is preferred that the suspending
elements comprise at least about 60 volume percent of the
superconducting material. It is even more preferred that the
suspending elements comprise at least about 70 volume percent of
superconducting material. In one preferred embodiment, the
suspending elements consist essentially of superconductive
material.
Such suspending elements may be connected to each other by
structural means which may, but need not contain, superconductive
material. Thus, referring to FIG. 5C, rods 55 need not consist of
superconductive material. Such suspending elements may be mounted
on a substrate which may be, but need not be, comprised of
superconductive material. Thus, referring to FIG. 5A,
superconducting squares 49 are mounted on a substrate which may be,
e.g., made of alumina insulator.
The superconducting material(s) which comprise said suspending
elements has a first critical field greater than about 10 Gauss. It
is preferred that such superconducting material have a first
critical field greater than about 100 Gauss. In one embodiment, the
first critical field of the superconducting material is greater
than about 500 Gauss.
The superconducting material(s) comprising the suspending elements
have a second critical field value of at least one Tesla. It is
preferred that the second critical field value of the
superconducting material be at least about 10 Tesla.
The critical temperature of the superconducting material used in
the suspending element(s) is at least about 35 degrees Kelvin. It
is preferred that such critical temperature be at least about 77
degrees Kelvin.
The superconducting material which comprises the suspending
element(s) has a flux penetration ratio of from about 0.01 to about
0.1. The flux penetration ratio of a material may be determined by
first forming the material into a circular plate with a diameter of
5 centimeters and a thickness of 3 millimeters. Then this plate is
exposed to an electromagnet with a field strength of 500 Gauss. The
tip of the electromagnetic pole is at a distance of 1 centimeter
above the center of the top face of the plate; and the
cross-sectional area of such tip is 0.5 square centimeter.
Consequently, the field applied in this test is confined to an area
of about 1 square centimeter around the center of the plate. A Hall
probe, obtained from Bell Communications Company of Florida, is
placed 1 centimeter away from the center of the opposing, lower
face of the circular plate, and the Hall probe is then electrically
connected to a Gauss meter obtained from the Bell Communications
Company of Florida; the extent to which the magnetic field
penetrated through the superconductive plate is then measured. The
flux penetration ratio is the ratio between the penetrative field
measured 1 centimeter below the bottom face of the plate to the
applied field, measured 1 centimeter above the top face of the
plate.
The stepper motor of this invention contains at least two primary
conductive elements. In one embodiment, said motor contains at
least 5 such conductive elements.
As used in this specification, the term primary conductive element
refers a conductive material which, preferably, is in the form of
wire. In one preferred embodiment, the conductive element is formed
via thermal vapor deposition technique. In yet another embodiment,
the conductive element is obtained by the thick film printing
technique. In yet another embodiment, conventional straight copper
wires obtained from Newark Electronic Company with a wire gauge
(AWG) of from about 10 to about 40 is used.
In the stepper motor of this invention, the primary conductive
elements are so disposed on or in the superconducting primary
suspending element so that each of such primary conductive elements
is separated from each adjacent primary conductive element by a
distance of from about 0.01 to about 10 millimeters. The term
adjacent, as used in this specification, refers to conductive
elements which are in the same plane and in substantially the same
direction. Thus, referring to FIG. 5, conductors 14 are adjacent to
each other, and conductors 42 are adjacent to each other, but
conductors 14 are not adjacent to conductors 42. The distance
between adjacent conductors 14 is from about 0.01 to about 10
millimeters. The distance between conductors 14 and 42 is not
always from about 0.01 to about 10 millimeters.
The conductive elements are generally electrically insulated from
each other. Thus, referring again to FIG. 5, although conductors 42
often lay on the top of conductors 14 at certain points, each of
these conductors is insulated by electrically insulative
material.
The stepper motor of this invention is comprised of at least one
magnetized article. The largest dimension of any such magnetized
article is less than about 1 centimeter.
The magnetized article(s) used in the stepper motor of this
invention has a magentic moment between the aforementioned first
critical field value (greater than 10 Gauss) and the second
critical field value (at least one Tesla).
The following examples are presented to illustrate the claimed
invention but are not to be deemed limitative thereof. Unless
otherwise stated, all parts are by weight and all temperatures are
in degrees centigrade.
EXAMPLE 1
16.95 grams of yttrium oxide (obtained from Alfa Products, Danvers,
Mass., Cat. no. 87829), 59.23 grams of barium carbonate (Fisher
Scientific Corp., Springfield, N.J., 1988 Catalog no. B30-500), and
35.82 grams of copper oxide (J. T. Baker Inc., Phillipsburg, N.J.,
Cat. no. 1814-01) were mixed using a ball mill. The wet ball
milling procedure consisted of placing the powders into a 500
milliliter plastic bottle, adding zirconia ball milling media,
adding enough distilled water as the liquid medium to make up a 50
weight percent solution, and placing it onto rollers revolving at
60 revolutions per minute to cause the zirconia media to tumble and
thoroughly mix the slurry of powder and distilled water. After 24
hours, the slurry was removed, and it was then dried at 80 degrees
centigrade for 5 hours until it was substantially bone dry. The
dried material was then ground in a mortar and pestle for 10
minutes to produce a fine, loose powder.
The ground powder mixture was calcined by setting the powder evenly
and loosely onto a zirconia setter, and placing the setter into a
furnace (Lindberg box furnace, model 10,549-110C, purchased from
the Fisher Scientific Company, Springfield, N.J., see page 539 of
1988 Fisher catalog) which was programmed for a specific firing
schedule. Starting at ambient temperature, the furnace was heated
to 925 degrees centigrade with a heating rate of 300 degrees
centigrade per hour. It was held at this temperature for 12 hours
and then allowed to cool to ambient at approximately 60 degrees per
hour. The entire calcination procedure occured under flowing oxygen
(10 cubic centimeters per minute).
The ball milling and calcination procedure was then substantially
repeated with the treated powder that was obtained from the first
heat treatment, with the exception that the distilled water was
replaced with hexane (Fisher Scientific Corporation, Cat. no.
H302-4). After the second calcination, the superconducting powder
was again ball milled, dried, and ground to obtain a fine and
advantageous particle size distribution, all of which occurred
substantially in the manner described above.
The treated powder was then sieved through a no. 325 mesh screen,
so that the resulting powder would have a particle size no greater
than 44 microns.
A sample of this sieved powder was analyzed to test its purity.
X-ray powder diffraction was conducted on a Siemens D-500
Diffractometer (model number C72298-A223-B-9-POZ-288, manufactured
by Siemens Company of West Germany) using copper alpha K-radiation
and a diffracted beam graphite monochrometer. Analysis revealed a
pure YBa.sub.2 Cu.sub.3 O.sub.7-x phase.
Compaction of the powder into the desired shape was accomplished
with a square, steel and brass die with internal dimensions of 1.83
centimeters by 1.83 centimeters. The die was a three part assembly
that is comprised of two shafts and a shaft housing. Approximately
3 grams of powder were placed into the die and pressed with 8,000
pounds per square inch of pressure, which gave a powder compaction
thickness of approximately 1.5 millimeters. After the pressing
procedure, an article with square dimensions, 1.83 centimeters per
side, was obtained.
The pressed article was then heated to 950 degrees centigrade in
the aforementioned Lindberg box furnace at a heating rate of 300
degrees centigrade per hour, held at this temperature for 24 hours,
cooled to 500 degrees centigrade at a rate of 100 degrees
centigrade per hour, maintained at this annealing temperature for
24 hours, and then allowed to cool to ambient temperature at the
end of the sintering procedure with a cooling rate of 60 degrees
centigrade per hour. The entire sintering procedure was conducted
under flowing oxygen (10 cubic centimeters per hour).
Due to the shrinkage occuring during the sintering procedure, the
resulting article had final surface dimensions of 1.59 centimeters
by 1.59 centimeters. The thickness shrinkage was less than 5
percent. A density of greater than 85 percent theoretical value
(6.4 grams per cubic centimeter) was achieved, and the proper
distribution of flux pinning sites was incorporated into the
structure.
The resulting YBa.sub.2 Cu.sub.3 O.sub.7-x sintered article was
tested for its purity and bulk superconducting properties. This was
accomplished by X-ray diffraction, resistance measurement, and
testing for the Meissner effect. A small sintered piece was used as
the X-ray diffraction target, and it was observed to be phase
pure.
The temperature of the superconducting transition, Tc, was
evaluated in accordance with the procedure described in a paper by
M. Pistakis and X. W. Wang, "Automated Superconductor Measurements
System," The Review of Scientific Instrum., 60(1), pages 135-136,
January, 1989. A Keithly current source providing about 1
milliampere to the sample (model number 228A, Keithly Instrument
Inc., Cleveland, Ohio) was used. A Keithly multimeter (model 195)
was used as a voltmeter to measure the voltage drop across the
superconducting sample due to the current. The resistance of the
sample at a given temperature is equal to the voltage divided by
the current. Another Keithly multimeter (model 196) was used as a
voltmeter for the thermocouple. The Tc of the material was 90
degrees Kelvin.
Testing for the Meissner effect was done by cooling the YBa.sub.2
Cu.sub.3 O.sub.7-x article below its superconducting transition
temperature with liquid nitrogen and placing a samarium cobalt
magnet (obtained from Edmund Scientific Company, 1989 Cat. no.
D33,168) on top of the article. The magnet displayed the necessary
Meissner levitation effect.
EXAMPLE 2
A linear superconductive motor platform, similar to that depicted
as 12 in FIG. 1, was produced from the sintered article described
in the example 1. The surface of the sintered article was polished
using 600 grit emery paper. Acetone (obtained from Fisher
Scientific Corporation, reagent number A18-1, Fisher 88 catalog)
was used during the polishing to rise and clean the surface of the
article.
Grooves were cut into the surface of the polished article to
provide places to lay conductors flush with the surface of the
article. A diamond saw (available from Motion Dynamics of New
Jersey) was used to cut such grooves. The grooves were 0.079
centimters wide and 0.079 centimeters deep, were separated from
each other by a distance of about 0.12 centimeters.
Epoxy resin (Type number 1266, manufactured by the Emerson and
Cumming Company of Massachusetts and sold by the Dean Company of
Ithaca, N.Y.) was inserted in the grooves. 30 AWG copper wire was
then inserted into the grooves; there was approximately 1
centimeter of extra wire on each side of the article to allow for
connection to the switching circuit.
EXAMPLE 3
A bidirectional platform, similar to that depicted in FIG. 5, was
constructed in substantial accordance with the procedure of Example
2. Perpendicular grooves were cut using the same spacings to obtain
the mesh pattern.
EXAMPLE 4
Two linear and one bidirectional superconductor motors were
constructed in substantial accordance with the procedures of
Examples 2 and 3, respectively. The motors were then attached to a
cooling chamber substantially identical to that chamber depicted in
FIG. 30; such attachment was made with epoxy containing silver
substances; and the motors were set next to each other, in a
substantially linear arrangement, with the bidirectional motor in
the center position.
The cooling chamber was filled with liquid nitrogen.
EXAMPLE 5
A Commodore computer (model VIC-20), two multiduplexors (obtained
from Jameco Electronics, Belmont, Calif., model number 74154),
thirty-two reed relays (obtained from Tandy Corporation of Fort
Worth, Tex., catalog number 275232, catalog number 432), thirty-two
NPN powder transistors (obtained from Newark Electronics Company,
Motorola MJ11032, page 59) two 1000-ohm 0.5 watt resistors
(obtained from Tandy Corporation, catalog number 271-023), and a 10
ampere 16 volt adjustable power supply (obtained from BK Precision
Company) were used to construct the circuit depicted in FIG. 29.
The circuit was housed in a protective cabinet with an output
connector (obtained from Newark Electronics, catalog number
81F5183) to make the connection to the conductors on the motors.
Each conductor was connected to its own switchable power
transistor.
The following software program was written in BASIC to provide
positve direct current voltage control signals to each of the
conductors.
__________________________________________________________________________
12 REM VARIABLES: 14 REM A - CURRENT ACTIVATED CONDUCTOR 16 REM B -
NUMBER OF CONDUCTORS TO BE ACTIVATED 18 REM CY - NUMBER OF MOTOR
RUNNING CYCLES 20 REM C1 - CURRENT RUN CYCLE 22 REM C2 - CONDUCTOR
TO BE SWITCHED ON 24 REM TI - INTERNAL CLOCK 26 REM XA -
CURRENT/VOLTAGE CONDUCTOR PULSE DURATION 28 REM XB - SWITCH OFF
DURATION 30 REM X1 - USER INPUT PULSE DURATION 32 REM X2 - USER
INPUT SWITCH OFF DURATION 34 REM SUBROUTINES: 36 REM 1000 -
CONDUCTOR OUTPUT CONTROL 38 REM
********************************************** 100
A=0,B=0,CY=0,C2=0,XA=0,XB=0,X1=0,X2=0 110 POKE 37136,255 120 POKE
37138,255 130 INPUT "ENTER NUMBER OF MOTOR CYCLES";CY 140 INPUT
"ENTER CONDUCTOR PULSE DURATION IN SEC.";X1 150 INPUT "ENTER SWITCH
OFF DURATION IN SEC.";X2 160 X1=X1*60 170 X2=X2*60 180 FOR C1 = 1
TO CY 190 GOSUB 1000 200 NEXT 210 POKE 37136,255 220 END 1000 READ
B 1010 FOR A = 1 TO B 1020 READ C2 1030 XA = X1 + TI 1040 POKE
37136,C2 1050 IF TI >= XA THEN POKE 37136,255: GOTO 1070 1060
GOTO 1030 1070 XB = X2 + TI 1080 IF TI >= XB THEN 1100 1090 GOTO
1045 1100 NEXT 1110 RETURN 2000 DATA
32,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16
17,18,19,20,21,22,23,24,25,26,27,28,29,30, 31,32
__________________________________________________________________________
The first number of the DATA statement (line 2000) represents the
number of activations per motor run cycle, and the following
numbers refer to the specific conductor that is to be switched on.
Each motor application may require different conductors to be
switched on sequentially; this may be accomplished by retyping line
2000 into that preferred arrangement.
By way of illustration, if one were to view the motor assembly of
Example 4, the conductors that were set parallel to each other from
left to right across the whole motor platform assembly were
numbered 1 to 24, and the perpendicular conductors on the middle
motor were numbered from 25 to 32 from top to bottom. Thus, to
obtain simple linear motion, which could find application in a mass
conveyor system, moving from left to right, line 2000 would read:
2000 DATA 24, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,
16, 17, 18, 19, 20, 21, 22, 23, 24.
EXAMPLE 6
Another application of the motor assembly and control mechanism
described in the example 5 can be a separation device. A screen
with two holes was placed between one linear motor and another
bidirectional motor. The screen was used for separating magnetic
materials, which was made of nonmagnetic material. An aluminum bar
of 1.59 centimeters length, 1.59 centimeters height, and 0.10
centimeters thickness was used. Two slots were cut into the bar
along its bottom width; one was the length between perpendicular
conductors 25 and 27, and it was 0.48 centimeters wide; and the
other was the length between perpendicular conductors 29 and 32,
and it was 0.68 centimeters wide. The height of each of the slots
was 1 centimeter. The screen was placed between the bidirectional
and the right linear motor, between parallel conductors 16
(bidirectional motor) and 17 (linear motor). Different sized
magnetic particles were then separated according to their maximum
dimensions across the poled faces of the particles (see FIG.
4).
The magnetic particles were placed at the upper left hand corner of
the left linear motor, where it was then stepped onto the
bidirectional motor, from left to right. The particle was then
oriented so that it was levitated approximately in the area defined
by vertical conductor 16 and perpendicular conductor 26. The rest
of the parallel conductors (17, 18 . . . ) were activated so that
the particle experienced a pulling force from left to right and was
collected at the top end of the right linear motor.
One of the particles had a size larger than 0.48 by 0.48 centimters
but smaller than 0.68 by 0.68 centimeters. This particle did not
pass through the hole in the screen which was 0.48 by 1.0
centimeter large. This particle was then stepped along the
perpendicular conductors (26, 27, 28, 29, 30, 31) to the area
defined by vertical conductor 16 and perpendicular conductor 31.
The conductors 17, 18, 19, 20, 21, 22, 23, and 24 were then
activated, and the particle was pulled through the second hole
defined by 0.68 centimeters by 1.0 centimeter.
The 2000 line of the program was changed.
It is to be understood that the aforementioned description is
illustrative only and that changes can be made in the apparatus,
the ingredients and their proportions, and in the sequence of
combinations and process steps as well as in other aspects of the
invention discussed herein without departing from the scope of the
invention as defined in the following claims.
In one embodiment, sensors are electrically, optically,
magentically, or operatively connected to various portions of the
stepper motor to determine the presence or absence of particles
therein or thereon. Suitable sensors include, e.g., magnetic pickup
coils, semiconductor sensors, and the like.
* * * * *